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Many texture images require the enhancement of coherent structures in various applications. Traditional coherence-enhancing diffusion filtering (CED) completes the interrupted lines and gaps but at the cost of reducing the contrast between coherent structures and the background. In this study, we introduce a source term into CED filtering to restore the initial image and the contrast lost by pure diffusion filters. Moreover, this new model combines contrast enhancement and diffusion processes, so it may be more suitable for dealing with white noise than the original CED. We assessed our method in terms of the theoretical and numerical properties changed by the source term. In our numerical assessment, we implemented our approach using an explicit scheme, which was accelerated by fast explicit diffusion. We compared the performance of our proposed approach with CED filtering based on fingerprint images. [ABSTRACT FROM AUTHOR]

We present a brand new method to construct the Schrödinger-like equations from a solution in this paper. Some Schrödinger-like equations with sources are derived by using a generalized solution, which have the form $$i\frac{\partial \Psi }{\partial x}+\frac{1}{2}\frac{\partial ^2\Psi }{\partial t^2}+|\Psi |^2\Psi +\alpha (x,t)\Psi +\beta (x,t)e^{ipx}=0$$ . The abundant analytical solutions of the Schrödinger-like equations are considered, including the bright rogue wave solution, dark rogue wave solution, Bell-shaped soliton solution, the interactions of two solitons, and other special soliton solutions. And we prove that the equation with source term has a weak solution. At last, the numerical simulations on the evolution and solitons collision of rogue wave solutions are performed to verify the prediction of the analytical formulations. The results could be of interest in such diverse fields as Bose-Einstein condensates, nonlinear fibers, and superfluids. [ABSTRACT FROM AUTHOR]

In this paper, we are concerned with shallow water flow model over non-flat bottom topography by high-order schemes. Most of the numerical schemes in the literature are developed from the original mathematical model of the shallow water flow. The novel contribution of this study consists in designing a finite difference weighted essentially non-oscillatory (WENO) scheme based on the alternative formulation of the shallow water flow model, denoted as “pre-balanced’’ shallow water equations and introduced in Rogers et al. (2003) [23]. This formulation greatly simplifies the achievement of the well-balancing of the present scheme. Rigorous numerical analysis as well as extensive numerical results all verify that the current scheme preserves the exact conservation property. It is important to note that this resulting scheme also maintains the non-oscillatory property near discontinuities and keeps high-order accuracy for smooth solutions at the same time. [ABSTRACT FROM AUTHOR]

Thick target bremsstrahlung source term for 450 MeV and 550 MeV electrons are experimentally determined using booster synchrotron of Indus facility at Raja Ramanna Centre for Advanced Technology, Indore, India. The source term is also simulated using EGSnrc Monte Carlo code. Results from experiment and simulation are found to be in very good agreement. Based on the agreement between experimental and simulated data, the source term is determined up to 3000 MeV by simulation. The paper also describes the studies carried out on the variation of source term when a thin target is considered in place of a thick target, used in earlier studies. [ABSTRACT FROM AUTHOR]

A full-scope method is constructed to reveal source term uncertainties and to identify influential inputs during a severe accident at a nuclear power plant (NPP). An integrated severe accident code, MELCOR Ver. 1.8.5, is used as a tool to simulate the accident similar to that occurred at Unit 2 of the Fukushima Daiichi NPP. In order to figure out how much radioactive materials are released from the containment to the environment during the accident, Monte Carlo based uncertainty analysis is performed. Generally, in order to evaluate the influence of uncertain inputs on the output, a large number of code runs are required in the global sensitivity analysis. To avoid the laborious computational cost for the global sensitivity analysis via MELCOR, a surrogate stochastic model is built using a Bayesian nonparametric approach, Dirichlet process. Probability distributions derived from uncertainty analysis using MELCOR and the stochastic model show good agreement. The appropriateness of the stochastic model is cross-validated through the comparison with MELCOR results. The importance measure of uncertain input variables are calculated according to their influences on the uncertainty distribution as first-order effect and total effect. The validity of the present methodology is demonstrated through an example with three uncertain input variables. [ABSTRACT FROM AUTHOR]

Source term is an important issue in safety assessment of nuclear power plants. Therefore, modeling of particulate concentration in reactor coolant systems during normal operation and hypothesized accidents is of continuing interest. We report here on exploration of a numerical solution of the Reeks-Hall equation with the use of the fractional resuspension rate in its original integral form. The numerical results for particulate concentration are compared with those obtained from the exact expression given by Williams and experimental data provided by Wells et al. The numerical results agree very well with exact results and also agree well with the data of Wells et al. Applications of the numerical method to problems with a time-dependent resuspension rate (for which exact solutions are not available) are explored, and some typical results are reported. The numerical method will be useful for verifying approximate techniques that are used for aerosol modeling in nuclear source term computer programs. [ABSTRACT FROM AUTHOR]

During a hypothetical severe accident in a nuclear reactor most of the radioactivity would be released from the damaged core and the broken primary circuit in the form of aerosols and chemical vapours and gases. However the effective radio-toxicity per unit release from the fuel depends both on the released mass and on the chemical form as well. The fission products release and transport in the circuit has been analysed for a Medium Break cold leg Loss Of Coolant Accident (MBLOCA) combined with the total loss of electric power supply (Station Black Out) for a reference PWR 1000 reactor using the severe accident integral code ASTECV1.3 rev2. A detailed description of the reactor model is given. Sensitivity analyses were performed in terms of break location and accumulator availability. The break location has an impact on the carrier gas temperature and in turn on the chemical speciation of the fission products. Also retention is influenced by the different flow pathways establishing in the circuit. The accumulator availability extends the duration of the core degradation process affecting the total production of hydrogen and the cumulative released mass of low, semi and highly volatile fission products. In agreement with the ASTEC equilibrium chemistry model, the Mo/Cs (Rb) molar ratio has the most influence on the fraction of iodine which can reach the containment in the gaseous or highly volatile form. Due to the surplus of Cs, the predicted dominant iodine species to the containment are CsI and its dimers. A 3–4% of iodine which reaches the break exists in gaseous (HI) and highly volatile metal-iodides (I 2 MoO 2 , SnI 2 , SnI 4 ) species. [ABSTRACT FROM AUTHOR]

Far field modelling of dredging induced suspended sediment plumes is important while assessing the environmental aspects of dredging. Realistic estimation of source terms, that define the suspended sediment input for far field dredge plume modelling, is key to any assessment. This paper describes a generic method for source term estimation as it is used in practice in the dredging industry. It is based on soil characteristics and dredge production figures, combined with empirically derived, equipment and condition specific ‘source term fractions’. A source term fraction relates the suspended fine sediment that is available for dispersion, to the amount of fine sediment that is present in the soil and the way it is dredged. The use of source term fractions helps to circumvent modelling of complicated near field processes, at least initially, enabling quick assessments. When further detail is required and extra information is available, the applicability of the source term fractions can/should be evaluated by characterisation monitoring and/or near field modelling. An example of a fictitious yet realistic dredging project demonstrates how two different work methods can trigger two distinctly different types of stress to the environmental system in terms of sediment concentration and duration. [ABSTRACT FROM AUTHOR]

In this letter, we propose a recursive finite-difference lattice Boltzmann model for the convection–diffusion equation (CDE) with a source term. The present model is derived directly from the evolution equation of the lattice Boltzmann (LB) method, and can correctly recover the CDE through the Taylor expansion. Compared with the classical LB method, the present model only involves one macroscopic variable, and thus requires less memory. We then conduct some numerical experiments. The results show that the present model could achieve comparable results to the LB method, and would be more accurate through adjusting some parameters properly. • A novel recursive finite-difference LB model for the CDE with a source term. • The present model only involves one macroscopic variable. • The present model would be more accurate than the classical LB model. [ABSTRACT FROM AUTHOR]

Radiological dispersion study is a key element in safety analysis report (SAR) of every nuclear facility for the purpose of emergency response planning. In this work, computational approach was used to determine the total effective dose and ground deposition at critical positions onsite and offsite of the Nigerian Research Reactor-1 (NIRR-1) facility which will be useful in the ongoing development of final SAR for NIRR-1 Low Enriched Uranium (LEU) core. In the methodology used, NIRR-1 LEU core was depleted with TRITON module of SCALE 6.2.3 code and the fission inventory in the core was calculated after a continuous operation at full power of 231.931 M W D / M T U for 918 Effective Full Power Days (EFPD) at an operation regime of 3 h per day, 3 days per week and 48 weeks per year. Hot Spot was employed for atmospheric transport and dose calculations with consideration of different accidental scenarios in which 20%, 30%, 60% and 100% gaseous inventory was hypothetically released into the atmosphere. From the results obtained, the total effective dose to maximum exposed workers at 10 m and maximum exposed members of public at 300 m from the reactor were 3.10 m S v a n d 0.43 m S v respectively for the worst-case scenario with 100% release while the maximum ground deposition was 5.5 × 10 6 B q / m 2 with corresponding maximum ground shine dose rate of 7.5 × 10 − 4 m S v / h r. This results are at least one order of magnitude below the dose limits recommended by the International Commission on Radiological Protection (ICRP) and indicate that the present LEU core of NIRR-1 is unlikely to cause any detectable health effect on workers and members of public in the event that 100% of its gaseous inventory is released into air in the environment. Hence it could unequivocally be said that the population is safe from the operation of NIRR-1 in its present location. • Radiological dispersion study is a key element in safety analysis report (SAR) of nuclear facilities. • Source terms for Nigeria Research Reactor-1 (NIRR-1) has been determined. • The total effective doses (TEDs) due to a release gaseous radionuclides were below the ICRP dose limits. • Ground shine dose rate was below the recommended public dose limit. • The air contamination after accident scenario was below UNSCEAR limit of unity. [ABSTRACT FROM AUTHOR]

The aim of this work is the modeling and simulation of in-containment fission products (FPs) quantification and behavior under loss of coolant accident (LOCA) in terms of NUREG-1465 key aspects. For this purpose, a kinetic model has been developed to determine the quantification and behavior of in-containment source term after loss of coolant accident for typical 1000 MWe PWR. A more realistic approach of continuous release of fission products from damaged core has been implemented with coolant retention. The simulation for in-containment fission product quantification influenced by containment atmosphere and containment system response has been carried out. Dramatic results have been obtained upon comparison study of fission product behaviors with different computational values. Moreover a contradiction in mixing rate ( w x ) value has been observed with a factor of 10 in comparison with Saeed et al. (2012). [ABSTRACT FROM AUTHOR]

As a result of the mass balance analysis for fission products (FPs) in the contaminated water accumulated in the Fukushima Daiichi nuclear power plant in the aftermath of the accident, it was concluded that the short-term cesium source was 50% of the total amount of cesium accumulated in the reactor, which was estimated with the SAMPSON severe accident analysis code, while the short-term source of tritium was 26% of the total tritium that was released during the U02fuel meltdown. The FP concentrations in the contaminated water during the 2 yr since the accident were determined by short-term FP sources, while their saturated concentrations, due to a balance between the release from the reactor and the cleanup, were determined by long-term FP sources. A multinuclei removal system, ALPS, has been operated at the plant to clean up the contaminated water to reduce FP concentrations to a level that is permitted for release to the environment. Tritium concentration in the contaminated water decreased a little during the 2 yr since the accident primarily from dilution by mixing groundwater rather than intentional removal. Industrial-scale removal of tritium from the huge amount of contaminated water is almost impossible using isotopic separation methods. Storage of tritiated water for a long period presents a high risk for leakage to the environment. As the most realistic procedure, the authors propose that the tritium be diluted with plenty of seawater to the natural background level and then be released into the ocean with continuous monitoring at the release point. [ABSTRACT FROM AUTHOR]

In order to identify the source term of gas emission in atmosphere, an improved hybrid algorithm combined with the minimum relative entropy (MRE) and particle swarm optimization (PSO) method was presented. Not only are the estimated source parameters obtained, but also the confidence intervals at some probability levels. If only the source strength was required to be determined, the problem can be viewed as a linear inverse problem directly, which can be solved by original MRE method successfully. When both source strength and location are unknown, the common gas dispersion model should be transformed to be a linear system. Although the transformed linear model has some differences from that in original MRE method, satisfied estimation results were still obtained by adding iteratively adaptive adjustment parameters in the MRE-PSO method. The dependence of the MRE-PSO method on prior information such as lower and upper bound, prior expected values and noises were also discussed. The results showed that the confidence intervals and estimated parameters are influenced little by the prior bounds and expected values, but the errors affect the estimation results greatly. The simulation and experiment verification results showed that the MRE-PSO method is able to identify the source parameters with satisfied results. Finally, the error model was probed and then it was added in the MRE-PSO method. The addition of error model improves the performance of the identification method. Therefore, the MRE-PSO method with adjustment parameters proposed in this paper is a potential good method to resolve inverse problem in atmosphere environment. [ABSTRACT FROM AUTHOR]

Highlights: [•] In the past, a disposal system was developed using a conservative reference spent fuel. [•] ASOURCE was used to exclude conservativeness in source terms of spent fuels. [•] Respective source terms of spent fuels were considered in a disposal system design. [•] Benefits were evaluated in terms of footprint reduction of a repository. [•] As a result, the footprint was decreased up to a roughly 50% [Copyright &y& Elsevier]

A finite-volume numerical method for studying shallow water flows over an arbitrary bed profile in the presence of external force has been proposed in [33]. This method uses the quasi-two-layer model of hydrodynamic flows over a stepwise boundary with advanced consideration of the flow features near the step. A distinctive feature of the suggested model is a separation of the studied flow into two layers in calculating the flow quantities near each step, and improving by this means the approximation of depth-averaged solutions of the initial three-dimensional Euler equations. We are solving the shallow-water equations for one layer, introducing the fictitious lower layer only as an auxiliary structure in setting up the appropriate Riemann problems for the upper layer. Besides, the quasi-two-layer approach leads to the appearance of additional terms in the one-layer finite-difference representation of balance equations. Numerical simulations are performed based on the proposed in [33] algorithm of various physical phenomena, such as breakdown of the rectangular fluid column over an inclined plane, large-scale motion of fluid in the gravity field in the presence of Coriolis force over amounted obstacle on the underlying surface. Computations are made for the two-dimensional dam-break problem on a slope precisely conform to laboratory experiments. The interaction of the Tsunami wave with the shore line including an obstacle has been simulated to demonstrate the efficiency of the developed algorithm in domains, including partly flooded and dry regions. [ABSTRACT FROM AUTHOR]

Highlights: [•] An atmospheric dispersion model for a hypothetical accident of Ghana Research Reactor-1 (GHARR-1) was developed. [•] Radiological safety analysis after the postulated accident was also carried out. [•] The MCNPX and HotSpot codes were used to achieve the objectives of our study. [•] All the values of effective dose obtained following the accident were far below the regulatory limits. [Copyright &y& Elsevier]

The purpose of this work is to draw attention to the plasma kinetics in a nitrogen-oxygen mixture. The model includes the plasma chemistry module and the circuit module investigating the electrical and the physical characteristics of high-pressure homogenous pulsed discharge. The fundamental chemistry governing ozone generation developed in this work is based on a full set of processes regrouped in 117 reactions involving 19 charged particles, atomic, and molecular species. The results of simulations show the temporal variation of the discharge electrical parameters and the effect of the voltage applied to ozone production. The role played by different reactions and species is also given by analyzing the time evolution of species concentrations, as well as the ozone production and loss terms. [ABSTRACT FROM PUBLISHER]

This paper presents an improved incompressible smoothed particle hydrodynamics (ISPH) method for wave impact applications. In most conventional ISPH techniques the source term of the pressure Poisson equation (PPE) is usually treated by either a density invariant or a velocity divergence-free formulation. In this work, both the density invariant and velocity divergence free formulations are combined in a weighted average form to determine the source term. The model is then applied to two problems: (1) dam-breaking wave impact on a vertical wall and (2) solitary wave run-up and impact on a coastal structure. The computational results have indicated that the combined source term treatment can predict the wave impact pressure and force more accurately compared with using either formulation alone. It was further found that depending on the application case, the influence of the density invariant and divergence-free parts could be quite different. For the more violent wave impact case, the divergence-free part played a more prominent role in ensuring accurate force simulations, while in less violent wave impact cases, the density invariant part seems to be more significant. A systematic parametric study has shown that the weighting coefficient in the PPE source term is independent of particle spacing under various wave impact situations. Also, a close relationship has been found between the ratio of flow height to length scales and weighting coefficient in the mixed pressure source term. [ABSTRACT FROM AUTHOR]

A new method of describing the liquid-gas phase transition is presented. It is assumed that the phase transition is characterized by a significant change of the particle density distribution as a result of energy supply at the boiling point that leads to structural changes but not to heating. Structural changes are described by an additional state characteristics of the system-the distribution density of the particles which is presented by an independent balance equation. The mathematical treatment is based on a special form of the internal energy and a source term in the particle balance equation. The presented method allows to model continua which have different specific heat capacities in liquid and in gas state. [ABSTRACT FROM AUTHOR]

Abstract: In this paper we consider the blow up at infinity of solutions for the integro-differential equation with strong damping term as well as a time dependent nonlinear dissipative function Q and a driving force term f, under the homogeneous Dirichlet boundary conditions. Some interesting applications are given in particular subcases of Q and f. This improves earlier results in the literatures. [Copyright &y& Elsevier]

Abstract: In this paper, we consider a semi-linear wave equation with damping and source terms. Using a potential well method, we prove the existence and uniqueness of global solutions of the wave equation and investigate uniform decay rates of solutions. Moreover, an example is given to illustrate our results. [Copyright &y& Elsevier]

A finite-volume numerical method for studying shallow water flows over an arbitrary bed profile in the presence of external force is proposed. This method uses the quasi-two-layer model of hydrodynamic flows over a stepwise boundary with advanced consideration of the flow features near the step. A distinctive feature of the suggested model is a separation of the studied flow into two layers in calculating the flow quantities near each step and thus improving the approximation of depth-averaged solutions of the initial three-dimensional Euler equations.We are solving the shallow-water equations for one layer, introducing the fictitious lower layer only as an auxiliary structure in setting up the appropriate Riemann problems for the upper layer. Besides, the quasi-two-layer approach leads to the appearance of additional terms in one-layer finite-difference representation of the balance equations. These terms provide the mechanical work done by a nonhomogeneous bed interacting with flow. A notable advantage of the proposed method is the consideration of the properties of the waterfall process, namely the fluid flow on the step in which the fluid does not wet a part of the vertical wall of the step. The presence of dry zones in the vertical part of the step indicates a violation of the hydrostatic flow conditions. The quasi-two-layer approach determines the size of the dry zone of the vertical component of the step. Consequently, it gives an opportunity to figureout the amount of the flow kinetic energy dissipation on the complex boundary. Comprehensive analysis and comparison of different methods for modelling shallow water flows in presence of an external force is provided. [ABSTRACT FROM AUTHOR]

Abstract: The secondary radiation field produced by seven different ion species (from hydrogen to nitrogen), impinging onto thick targets made of either iron or ICRU tissue, was simulated with the FLUKA Monte Carlo code, and transported through thick concrete shields: the ambient dose equivalent was estimated and shielding parameters evaluated. The energy for each ion beam was set in order to reach a maximum penetration in ICRU tissue of 290mm (equivalent to the therapeutic range of 430MeV/amu carbon ions). Source terms and attenuation lengths are given as a function of emission angle and ion species, along with fits to the Monte Carlo data, for shallow depth and deep penetration in the shield. Trends of source terms and attenuation lengths as a function of neutron emission angle and ion species impinging on target are discussed. A comparison of double differential distributions of neutrons with results from similar simulation works reported in the literature is also included. The aim of this work is to provide shielding data for the design of future light-ion radiation therapy facilities. [Copyright &y& Elsevier]

Abstract: Following the Fukushima nuclear power plant accident detections of 133Xe have been made in various locations. Using results of these remote measurements the Fukushima 133Xe source term has been reconstructed and compared with previously reconstructed 137Cs and 131I source terms. The reconstruction is accomplished by applying atmospheric transport modeling and an adapted least square error method. The obtained results are in agreement with previous estimations of the Fukushima radionuclide source, and also serve as a proof of principle for source term reconstruction based on atmospheric transport modeling. [Copyright &y& Elsevier]

Highlights: [•] Deterministic and probabilistic approaches are used for Source Term evaluations. [•] The Phébus FP results contribute to improve the Source Term evaluations for PWRs. [•] Iodine and ruthenium behavior have a large impact on the Source Term consequences. [•] Iodine oxide seems to be one of the major iodine species in releases. [ABSTRACT FROM AUTHOR]

Highlights: [•] Prototypicality of Phebus is unique for severe accident integral code assessment. [•] MELCOR and SCDAP show good simulation capability. [•] Phebus revealed knowledge gaps concerning organic iodine source. [•] Complementary studies seek to reduce uncertainties. [•] New engineering technology is developed to resolve organic iodine issue. [ABSTRACT FROM AUTHOR]

Highlights: [•] Presentation of the scientific objectives of the Phébus FP experimental programme. [•] Description of the bundle, the circuit and the containment in the Phébus facility. [•] Presentation of the instrumentation for on-line and post-test measurements. [•] Description of the test conduct and experimental conditions for all the tests. [ABSTRACT FROM AUTHOR]

Highlights: [•] Presentation of the objectives of Phébus FP programme of integral experiments. [•] Key results on core degradation concern cladding oxidation and fuel relocation. [•] Key findings on fission product concern release, transport, iodine chemistry. [ABSTRACT FROM AUTHOR]

Highlights: • Estimation of source terms for I-131 and Cs-137 for Fukushima Daiichi NPP. • Simplified Gaussian puff based atmospheric dispersion model is used. • Good agreement of estimated values as compared to that given by NISA, TEPCO and IRSN. [Copyright &y& Elsevier]

We report here the additive Runge-Kutta methods for computing reactive Euler equations with a stiff source term, and in particular, their applications in gaseous detonation simulations. The source term in gaseous detonation is stiff due to the presence of wide range of time scales during thermal-chemical non-equilibrium reactive processes and some of these time scales are much smaller than that of hydrodynamic flow. The high order, L-stable, additive Runge-Kutta methods proposed in this paper resolved the stiff source term into the stiff part and non-stiff part, in which the stiff part was solved implicitly while the non-stiff part was handled explicitly. The proposed method was successfully applied to simulating the gaseous detonation in a stoichiometric H/O/Ar mixture based on a detailed elementary chemical reaction model comprised of 9 species and 19 elementary reactions. The results showed that the stiffly accurate additive Runge-Kutta methods can capture the discontinuity well, and describe the detonation complex wave configurations accurately such as the triple wave structure and cellular pattern. [ABSTRACT FROM AUTHOR]

In 2011 the IRSN conducted several assessments of atmospheric radioactive releases due to the Fukushima Daiichi NPP accident (March 11, 2011) and of their impact on Japan's terrestrial environment. They were based on the IRSN's emergency management tools and on the abundant information and technical data gradually published in Japan. According to these assessments, the main release phase lasted from March 12 to 25, 2011 and impacted Japanese land in two events, the first on 15 and 16 March, in which the main radioactive deposits were formed, and the second from March 20 to 23, which was less significant. The highest amounts of radioactive deposits were found in an area extending upwards of several tens of kilometers northwest of the plant. Lower amounts were discontinuously scattered in an area extending up to over 250 km away. Initially composed mainly of short-lived radionuclides, the deposits' activity sharply decreased in the subsequent weeks. Since the summer of 2011, cesium-134 and cesium-137 have become the residual deposits' main components. According to IRSN estimates, in the absence of protection, the doses due to exposure to the radioactive plume during the atmospheric release phase may have been potentially higher for people who remained in coastal areas up to several tens of kilometers north and south of the damaged plant. Thereafter, people living up to 50 km northwest of the plant, outside the 20-km emergency evacuation zone, were potentially most vulnerable to residual radioactive deposits over time. [ABSTRACT FROM AUTHOR]

The goal of this work is to study a model of the viscoelastic wave equation with nonlinear boundary/interior sources and a nonlinear interior damping. First, applying the Faedo-Galerkin approximations combined with the compactness method to obtain existence of regular global solutions to an auxiliary problem with globally Lipschitz source terms and with initial data in the potential well. It is important to emphasize that it is not possible to consider density arguments to pass from regular to weak solutions if one considers regular solutions of our problem where the source terms are locally Lipschitz functions. To overcome this dificulty, we use an approximation method involving truncated sources and adapting the ideas in [13] to show that the existence of weak solutions can still be obtained for our problem. Second, we show that under some restrictions on the initial data and if the interior source dominates the interior damping term, then the solution ceases to exist and blows up in ?nite time provided that the initial data are large enough. [ABSTRACT FROM AUTHOR]

Abstract: This work investigates stability of an inverse problem for a backward linear parabolic heat problem by using an initial temperature measurement. This kinds of problem has been widely used in a various field of pure and applied science. The necessary condition of the minimizer for the cost functional are constructed by using the optimal control theory. Stability of the minimizer for the cost functional is proved based on the necessary condition. [Copyright &y& Elsevier]

Abstract: During the severe accidents in a commercial nuclear power plant (NPP) large amount of fission products releases into the containment with the accident progression, which includes in-vessel and ex-vessel sources. In a severe accident, evaluation of the source term is demanding to alleviate the radiological hazards to public risk. Source term countermeasures to containment states are studied for two-loop 2720MWt PWR considering TMI 2 reactor as the reference reactor. SBO, LOCA, SBLOCA and Feedwater accidents are selected as the typical accidents initiating severe accidents. For post 1100 reactor operation days, the core inventory is calculated under core design constrains. A MATLAB program is developed for modeling and simulation of release of radioactivity that use core inventory. Runge–Kutta method and Simpson Rule have been implemented for numerical simulation. Assuming in-vessel and instantaneous release of radioactivity into the containment, simulation outcomes are verified for noble gasses. For noble gasses, iodine, cesium, and for Aerosols, the release rates are studied in normal, emergency and isolation state of containment. The source term value shows rapid increase followed by an approach towards saturation as the exhaust rate value increases. The radioisotope’s dependency on exhaust rate and containment retention factor (CRF) is also studied. [Copyright &y& Elsevier]

Abstract: Regional-scale atmospheric dispersion simulations were carried out to verify the source term of 131I and 137Cs estimated in our previous studies, and to analyze the atmospheric dispersion and surface deposition during the Fukushima Dai-ichi Nuclear Power Plant accident. The accuracy of the source term was evaluated by comparing the simulation results with measurements of daily and monthly surface depositions (fallout) over land in eastern Japan from March 12 to April 30, 2011. The source term was refined using observed air concentrations of radionuclides for periods when there were significant discrepancies between the calculated and measured daily surface deposition, and when environmental monitoring data, which had not been used in our previous studies, were now available. The daily surface deposition using the refined source term was predicted mostly to within a factor of 10, and without any apparent bias. Considering the errors in the model prediction, the estimated source term is reasonably accurate during the period when the plume flowed over land in Japan. The analysis of regional-scale atmospheric dispersion and deposition suggests that the present distribution of a large amount of 137Cs deposition in eastern Japan was produced primarily by four events that occurred on March 12, 15–16, 20, and 21–23. The ratio of wet deposition to the total varied widely depending on the influence by the particular event. [Copyright &y& Elsevier]